The narration of the opening titles reveals that the Butler
family was in the Amazon for their river rafting trip. The
Amazon is a large rainforest in the northern part of South
America. Since evidence through the series indicates the
Butlers are still on modern Earth, the lost valley in which
they find themselves must be within the Amazon rainforest
and not the prehistoric past or on another world. The
location may have been inspired by that of the Lost World,
from the 1912 Arthur Conan Doyle novel of the same name, on
a plateau (rather than a valley) in the Amazon jungle.

The opening titles of the series declare that the Butler
family has been flung into "a world that time forgot." This
is a reference to the 1918 short novel The Land That
Time Forgot by Edgar Rice Burroughs, with a similar
theme, about a submarine that emerges from the sea into a
land of prehistoric creatures.

In "S.O.S." we learn that the
pool of water from which the Butlers' raft surfaced into the
Valley of the Dinosaurs is called by the cave dwellers,
the Black Lagoon. Possibly the writers were inspired by the
1954 classic creature film, The Creature from the Black
Lagoon, which takes place in the Amazon, as does
Valley of the Dinosaurs.

At 0:37
during the opening titles, the sauropod dinosaur depicted is probably meant
to be a Brontosaurus (now known as Apatosaurus).

At 0:48 during the opening titles, the
dino depicted is presumably a Stegosaurus, with
alternating plates along its spine.

As the Butler family is hauled up the cliff face on a rope
by Gorok's clan at 0:54 in the opening titles, notice that
the family dog, Digger, is also borne aloft, on John's right
shoulder.

At 0:58
in
the opening titles, notice that there are
two large birds and the thigh and
shank of a hoofed animal hanging on
the cave wall in anticipation of a
future meal. Painted on the wall are
renderings of a mammoth, a deer or
elk, a bison, a predatory beast, and
what looks like the horns of a
moose. John is inspecting a large
tusk, probably from a mammoth, with Gara.

A dinosaur (Brontosaurus) roars into the POV of the
viewer at the end of the opening titles, just as a
Tyrannosaurus does
in the opening of
Land of the Lost.

Besides the foreground
Brontosaurus, notice there are a couple
others in the water in the background behind the Valley
of the Dinosaurs logo and one of the beasts dips its head under
the water and back up as the announcer proclaims the series'
title.